Gauge



Nov. 24, 1942.

H. THOMASON GAUGE Filed u 15, 1940 -INVENTOR, fif/ l/ r ,EY

.Illl

ATTORNEY Patented Nov. 24, 1942 UNITED sTATEs PATENT,

OFFICE 1 Claim.

defining the braking surface of an arcuate brake shoe, or of the arcuate support for the brake lining. Such brake shoes necessarily cover much less than 180 of arc. objects of this invention to make it possible to determine the diameter or radius of an arc of less than 180 in a simple and rapid manner.

This object is accomplished by the provision of a pair of plane surfaces placed at an angle to each other and capable of being respectively placed in tangency with points on the arc to be measured. The smaller the diameter of theatre, obviously the closer the arc can approach the place of intersection of the tangent surfaces. This feature is utilized for the gauging operation.

Accordingly a movable gauging surface can be made to contact the are on a point falling on the bisector of the angle between the planes. The position of the gauging surface when it is thus moved into contact with the arc is a function of the radius (or diameter) of the arc. The angle between the tangent surfaces determines the minimum arc that can be simultaneously placed in tangent contact with both surfaces.

It is accordingly another object of this invention to make it possible to utilize tangent plane surfaces and a movable gauging surface adapted to contact the arc, for obtaining measurements of diameters or radius.

By placing the arcuate member to be gauged in tangent relation to the surfaces and moving the member angularly, out-of-round conditions i are readily detected by a corresponding movement of the gauging surface along the bisector.

If the arc of the member being gauged forms an arc of a perfect circle, the position of the gauging surface does not vary. 7

It is accordingly another object of this invention to make it possible to detect an out-o'f-round condition, and to gauge the extent-of departure from a perfect circular arc.

This invention possesses many other advantages, and has other objects which may be made more easily apparent from a consideration of one embodiment of the invention. For this purpose there. is shown a form in the drawing accompanying and forming part of the present It is accordingly one of the specification. This form will now be described in detail, illustrating the general principles of the invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of this invention is best defined by'the appended claim.

Referring to the drawing:

Figure 1 is a-plan view of a gauge incorporating the invention, and shown in use;

Fig.2 is an enlarged fragmentary View similar to Fig. 1, but with the cover removed;

Fig. 3 is a sectional view taken along plane 3-3 ofFigZ; Y

Fig. 4 is an enlarged sectional view taken along plane 4-4 of Fig. 2;

Fig. 5 is a sectional view'taken along plane 5-5 of Fig. 2';

Fig. 6 is a sectional view taken along 6-6 of Fig. 4; and I Fig.- '7 is a diagram by the aid of which the mode of operation of the gauge may be described.

The gauging of external diameters of arcs of plane less than 180 by the aidof the apparatus here-' inafter tobe described, involves the use of a pair of plane surfaces I and, 2. These plane surfaces I and 2 as illustrated in the diagram ofFig. '7, converge to intersect at the point 3. The angle between the plane surfaces I and 2 may be chosen of any suitable value. In the present instance this angle is slightly in excess of A circular object 4 may be placed so that its external circular periphery is tangent to both of. the surfaces I and 2. In the case of an article 5 having a diameter larger than object 4, the points of tangency'are farther removed from the intersection 3. We shall now assume that a bisector 6 of the angle between the planes I and 2 is drawn. This bisector must pass through the center of the arc being gauged. The distance D from point 3 to the point of intersection I of arc of the object 4 and bisector 6 is a function of the radius or diameter of the' arc. The distance D corresponds to the length of the bisector 6 between the points 3 and 8, this latter point ,8 representing'the intersection of bisector 6 with the arc of article 5. The larger thefarc being measured, the greater this distance becomes. I In the gauging apparatus'clisclosed in Figs. 1 to 6 inclusive, the plane surfaces I and 2 are shown as formed, as by appropriate machining, on arms 9 and I0 respectively. These 'arms are formed in this instanceas integral portions of a cast housing II. This housing I I is provided with a'peripheral flange. 50 forming a circular recess the bolt 22.

direction of the bisector 6. The surface I3 is thus adapted to contact the outer periphery of the are being gauged. In Fig. 1, the are being gauged is formed for example by a brake liner I4 supportedon an arcuate brake shoe I5.

The gauging member I2 is shown as guided for accurate movement along the bisector 6 by the aid of a pair of spaced walls I6 and I1 integral with the casing II and projecting from the bottom I8 thereof (Figs. 3 and The flange -50 of the housing II is appropriately slotted as indicated at I9 (Fig. 2) for permitting the gauging member I2 to pass downwardly and out of the casing II. A plate 2|] may be fastened across the top of the walls I6 and II to confine the gauging member |2 against transverse movement with respect to the bisector 6.

The gauging member I2 is urged continuously by a resilient means into contact with the arcuate surface being gauged, therebeing stops appropriatelyformed within the casing II for limiting the motion of the gauging member I2.

There is fastened to the top of the member I2 a bar 2| of general rectangular section. (Figs. .2, 3 and 4). 2| may be fastened together as by the aid of If desired, a dowel pin 23 (Fig. 3) may be utilized to maintain the gauge member I2 and the bar 2| in proper alinement. Furthermore, the lower end of bar 2| may be accommodated in a shallow slot 29 formed adjacent the upper edge of the gauge member I2. The upper end of the bar 2| is shown as guided in the boss 24 projecting from the bottom of the casing II. of member 2| are plane for forming an accurate guiding surface. A tension spring 25 operates on the bar 2| to urge it downwardly. For this purpose one end of the spring 25 is anchored in the stationar anchor 26 formed on the inner The gauge member I2 and the bar I,

The right hand and bottom faces -ed in a cover 4|. The cover 4| may be provided surface of the flange I2 (Fig. 2). The upper end of the spring 25 is anchored to a pin 21 extending transversely of the member 2| adjacent the top thereof. The lower face of bar 2| acts as a stop against the walls I6 and I1, limiting the downward movement of the gauging member I2.

When the gauge is in the inactive position with no arcuate member being-gauged, the spring 25 pulls the member l2 to the limiting position illustrated in Fig. 2. When an article such as the brake lining I4 is urged into tangent contact with surfaces I and 2, the surface I3 is engaged by the arcuate brake lining and the gauge member I2 is moved upwardly against the pressure of spring 25. The position of surface I3 when tangency occurs between the liner I4 and surfaces I and 2 is indicative of the radius or diameter of the are being gauged.

By appropriate indicating mechanism, the position of the gauge member I2 may be caused to indicate the diameter of the are being gauged. Forthis purpose movement of the bar 2| is translated into a movement of rotation. Thus the left hand edge of the bar 2| may carry gear teeth 28 forming a rack. These gear teeth engage a pinion 30. As shown'most clearly in Fig. 3 this pinion 30 may be appropriately formed integrally with a flange 3| and is rotatable about a stationary stub shaft 32. This stub shaft 32 is press fitted into the boss 24. The flange 3| has fastened to it a dial structure 33 having a scale portion 34 adjacent its periphery. This scale portion may be formed on a paper facing 35 (Fig. 4) clamped between the disks 36 and 31.

with a flange 42 overlying the flange 50. The cover 4| may be fastened to the housing I by the aid of a plurality of screws 43. It may readily be shown that the scale diversions on the scale are uniform.

In order to restrain axial movement of the pinion 30, the stub shaft 32 may be provided at its upper end with a cotter pin 44. Furthermore, in order to eliminate any backlash between teeth 28 and pinion 3U, resilient take-.up means may be provided. This is shown most clearly in Figs. 4 .and 6. Thus a clock spring 45 may be disposed in a recess 46 in the upper surface of the flange 3|. The inner end of the clock spring is accommodated in a slot formed in the stationary stub shaft 32. Its outer end 4! extends substantially radially into a slot 48 formed radially of the flange 3|. This clock spring 45 tends to rotate the pinion 30 in a clockwise direction as viewed in Fig. 6, and keeps the teeth of the pinion 30 against'the upper tooth surfaces of teeth 28.

The mode of operation of the apparatus is apparent fromthe foregoing. When the member to be gauged is placed into the position illustrated in Fig. 1, the gauging member I2 is constrained to move along the bisector 6. The gauging surface I3 is maintained in contact with the arc to be measured by the force of the spring 25. The smaller the radius of the arc to be measured, the farther upwardly will the gauge member I2 be moved. The gauging position of Fig. 1 causes the scale 34 to asume a definite angular position and .the indicated diameter can be read off through ,the window 39 by the aid of the pointer 38.

By moving the member I5 angularly so that diiferent points in succession are in tangency with plane surfaces and 2, an out-of-round condition can be detected. This would be indicated by movement of the dial 34.

As regards the choice of the angle-betweenthe plane surfaces and 2, the.larger thisangle, the

smaller is the arc intercepted between the points means forming a pair of plane surfaces diverging-at a fixed angle, a gauging memberhaving a gauging surface and adapted to move along a linear direction included within the angle, a dial,

.a rotary hub for supporting the dial, a stationary post upon which said hub is mounted, a gear car- .ried by the hub and rotatable coaxially therewith,

a rack member carried bythe gaugingmember andcooperating with said gear, said hub having a radial slot, and a spiral spring anchoredat its inner end to the post and havingits outer end engaged in said slot.

-HJALMAR THOMASQN. 

